Multiple pieces of piping stacked on top of each other with a clouded over sky in the background

The real inside story on our pipelines

In-line inspection technologies – such as acoustic resonance technology (ART) and electro-magnetic acoustic transducers (EMAT) – could help National Grid build a better understanding of the condition of its pipelines. Project Engineer, Kirsty McDermott explains how new research by the business into these previously untried tools is set to optimise costs and minimise disruption for gas consumers.

Our Gas Transmission business operates and maintains every centimeter of the 7,660km of high-pressure pipeline that runs beneath your feet. To keep the network healthy and the gas flowing, we need to have a thorough understanding of the condition of our assets. In-line pipe inspection plays an integral role in this.

Current techniques are based on magnetic flux leakage (MFL) technology. While this is highly developed and understood, it indirectly measures pipe-wall thickness. This brings a degree of uncertainty to our results.

We’re keen to improve our understanding in this area, so we’ve been exploring new tools and technologies – through two Network Innovation Allowance (NIA) funded projects – that could support our existing ways of working and help us improve how we manage our assets.

We’ve been exploring new tools and technologies that could support our existing ways of working and help us improve how we manage our assets.

- Kirsty McDermott, Project Engineer

Making the right calls on maintenance

Innovating in this area is important, because improving the accuracy of inspections allows us to develop a more informed strategy for how we manage our assets. More robust results will also help us avoid unnecessary excavations. This brings financial benefits and means less disruption for our customers.

One of the main tools we’ve been exploring is acoustic resonance technology (ART). The in-line inspection device uses ultrasonic techniques to accurately find and measure features on a pipe. This provides precise information, allowing us to make the efficient decisions on repairs and replacement that I touched on before.

We identified ART as a potential addition to our toolbox of technologies because it promises a very high accuracy of +/-0.2mm when measuring the thickness of pipe walls. It can also cope with a high range of gas flows. This is good news for our control room engineers and consumers as it means we’re less likely to need to adjust flow rates when the tool is running.

Another potential strength is ART’s ability to spot areas where pipeline coatings have disbonded. This is important data for us, because it points to the possibility of corrosion.

Drawing conclusions with ART

We trialled ART on one of our pipelines in Scotland earlier in the year, with the tool used on a 45km section. In the first week of November, we’re putting the technology through its paces on a second run to see if it can deliver the level of performance and data that we expect.

If successful, we’ll consider using the technology to support the work done by MFL.

We’ve also been looking at electro-magnetic acoustic transducer (EMAT) technology to see how other technologies might support our inspection work. EMAT is known for being good at identifying a wide range of defects, including disbonded coating and cracking, and we’ll be putting it to the test during an exciting few weeks of data collection in November.

Across three weeks, we’ll first run our standard MFL inspection tool, which we regularly use on this section of line. The following week, the EMAT tool will take its place to show us how it performs. And finally, ART will be deployed to show us its capabilities.

It will be an exciting and valuable time for us, bringing a quantity and quality of data about pipeline condition unmatched on any UK pipeline, and probably anywhere in the world.

Step change in pipeline inspection

So we’re on the cusp of making important progress in pipeline inspection. As we learn more, we’ll be in a great position to make significant changes in how we inspect and manage our network.

Over the past three years, in-line inspections have spotted several hundred features that required action, such as excavation and repair. Yet the resulting digs showed us that 25% of these didn’t require excavation.

By developing a wider range of technologies – where a particular tool is appropriate for specific conditions, such as flow rates, condition of pipe or feature type – we believe we can achieve more targeted excavations.

We’ll make more informed asset management decisions and avoid needless disruption and costs for consumers.